/*
 * Copyright (c) 2004-2022, University of Oslo
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 * Neither the name of the HISP project nor the names of its contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.hisp.dhis.webapi.controller;

import java.io.IOException;
import java.io.StringWriter;
import java.io.UncheckedIOException;
import java.io.Writer;

import org.hisp.dhis.common.DhisApiVersion;
import org.hisp.dhis.webapi.mvc.annotation.ApiVersion;
import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import io.prometheus.client.CollectorRegistry;
import io.prometheus.client.exporter.common.TextFormat;

/**
 * @author Luciano Fiandesio
 */
@Profile( "!test" )
@Controller
@ApiVersion( { DhisApiVersion.DEFAULT, DhisApiVersion.ALL } )
public class PrometheusScrapeEndpointController
{
    private final CollectorRegistry collectorRegistry;

    public PrometheusScrapeEndpointController( CollectorRegistry collectorRegistry )
    {
        this.collectorRegistry = collectorRegistry;
    }

    @GetMapping( value = "/metrics", produces = TextFormat.CONTENT_TYPE_004 )
    @ResponseBody
    public String scrape()
    {
        try
        {
            Writer writer = new StringWriter();
            TextFormat.write004( writer, this.collectorRegistry.metricFamilySamples() );
            return writer.toString();
        }
        catch ( IOException ex )
        {
            // This never happens since StringWriter::write() doesn't throw
            // IOException

            throw new UncheckedIOException( "Writing metrics failed", ex );
        }
    }
}
